First off, let’s take a look at how this project, which resulted in this Online Book, started.
About eight years ago, we switched to Absorbed Glass Mat (AGM) batteries on Morgan’s Cloud, to get the following benefits over liquid filled lead-acid batteries:
- Shorter recharge times since AGM batteries accept a faster charge rate.
- No risk of the batteries freezing when we lay-up the boat unattended since AGM batteries have a very low self-discharge rate. (A fully charged battery won’t freeze but a flat one will.)
- About 10% more capacity in the same size battery.
However, our experience with AGM batteries was not good: We went through four sets of house batteries from two different manufacturers after the switch to AGM. When you consider that AGM batteries are as much as double the price of liquid filled batteries, that stung.
In the process of solving that problem, we learnt a huge amount that can be applied to the care of any lead-acid battery.